# Regarding residue not found in rtp

**URL:** <https://gromacs.bioexcel.eu/t/regarding-residue-not-found-in-rtp/6860>\
**Category:** User discussions\
**Tags:** forcefield\
**Created:** [July 19, 2023, 4:33am UTC](https://gromacs.bioexcel.eu/t/regarding-residue-not-found-in-rtp/6860 "2023-07-19T04:33:31Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![ashkhan](https://avatars.discourse-cdn.com/v4/letter/a/76d3ee/32.png) [@ashkhan](https://gromacs.bioexcel.eu/u/ashkhan)\
**Post date:** [July 19, 2023, 4:33am UTC](https://gromacs.bioexcel.eu/t/regarding-residue-not-found-in-rtp/6860/1 "2023-07-19T04:33:31Z")

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GROMACS version: 2022  
GROMACS modification: Yes/No  
Here post your question  
Dear users,  
I have added the Co+2 parameters in ffnonbonded.itp, atomtypes, ions.itp and aminoacids.rtp in forcefield amber99sb-ildn but it is still showing the error that residue CO not found in residue topology database. I have also checked the residue name, atom name and atom types correctly. Anybody can suggest me regarding this.

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**Author:** ![Karis](https://avatars.discourse-cdn.com/v4/letter/k/ed8c4c/32.png) [@Karis](https://gromacs.bioexcel.eu/u/Karis)\
**Post date:** [July 20, 2023, 6:12am UTC](https://gromacs.bioexcel.eu/t/regarding-residue-not-found-in-rtp/6860/2 "2023-07-20T06:12:20Z")

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Could you provide more detail on how you setup the parameters (where you got the parameters, exactly what lines were added to which files, how you setup the topol.top file, etc)?